EVSE standards engineers envisioned AC charging to be the lowest barrier of adoption possible. And I think they succeeded! However, some charging boxes are still (unreasonably?) expensive or have very few features, and it's hard/expensive to find open source/flashable ones yet. How can we bridge the gap?

My use case features a low-energy house with 2.2kW energy availability, and I wanted to ensure the car plus appliances did not go over the limit. Using an off-the-shelf smart charger was unreasonable due to cost, installation requirements and expected savings.

Instead, I built my own watt-meter using ESP32 and Rust, a backend to track the energy expenditure, and an out-of-band mechanism to talk to the car.

I'll explore the trade-offs to the different options you have to talk to the EV (ISO 15118, IEC 61851-1 and vendor API if available), and present the repos that made the current iteration possible.

I'll also talk about alternatives (having a Matter-enabled Watt-meter) and future work that could be welcome,including the current reliance on a non-vendor-neutral API.

Wattmeter code: https://github.com/ssaavedra/esp32-amp-sensor Backend: https://github.com/ssaavedra/amp-sensor-backend